Molding apparatus for reflectors



Jan. 16,` 1968 P. HEDGEWICK ETAL 3,363,875

MOLDING APPARATUS FOR REFLECTORS Original Filed Dec. 5, 1963 5Sheets-:Sheet 1 I I l l l I z I I 38 3.5' 30" 4 INVENTORS PETERHEDGEWICK WALLACE A. STANLEY ATTORNEYS Jan. 16, 1968 P. HEDGEWICK ET AL3,363,875

MOLDING APPARATUS FOR REFLECTORS Original Filed Dec. 5, 1963 5Sheets-Sheet 2 d" e L l INveNTors PETER HEnGEwlcK ATTORNEYS' Jan. 16,1968 P. HEDGEW|CK ETAI- MOLDING APPARATUS FOR REFLECTOHS 5 Sheets-Sheet5 Original Filed Dec.

INVENTORS PETER HEDGEWICK WALLACE A. STANLEYv Jan. 16, 1968 P. HEDGEWICKET AL l MOLDING APPARATUS FOR REFLECTORS 5 Sheets-Sheet 4 original FiledDec.

ZEE-H' l-mzl mig@ ZEE-ELL INVENTORS PETER HEDGEWICK WALLACE Ai STANLEYATTORNEYS Jan. 16, 1968 P. HEDGEWICK ETAL ,3,363,875

A MOLDING APPARATUS FOR REFLECTORS Originalr Filed Dec. 5, 1963 I 5Sheets-Sheet 5 INVENTORS PETER HEDGEWBCK WALLACE A. lSTANLEY ATTORNEYSMymfMm/Lm United States Patent Oilice 3,363,875 MOLDING APPARATUS FRREFLECEORS Peter Hedgewick, 2375 Windermere Read?, Windsor, @n-

tario, Canada, and Wallace A. Stanley, 52M Winlane Drive, BloomfieldHills, Mieli. 486113 Original application Dec. 5, 1963, Ser. No.,328,333, new Patent No. 3,258,840, dated July 5, 1966. Divided and thisapplication Feb. 7, 1966, Ser. No. 525,766

I3 Claims. (Cl. 249-117) This application is a division of ourco-pending application Ser. No. 328,333, filed Dec. 5, 1963, now PatentNo. 3,258,840.

This invention relates to molds for reflecting devices and particularlyto reflectors for use on automotive vehicles, along highways, airfieldstrips, and the like.

The invention particularly relates to molds for reflectors of the typeused on automotive vehicles which are formed from plastic or glass andproduce a reflective brilliance designated as Class A and Class B inaccordance with the standards of Society of Automotive Engineersdesignated SAE 1594er.

The generally accepted method of making such reflectors is by injectinga charge of molten material, such as plastic, between a core and a moldconsisting of a cluster of oriented hexagonal rods having ends shapedpreferably in the form of a cube. The brilliance of the resultantreilector depends upon the accuracy With which the cubed ends of therods in the cluster are formed. In order to maintain the high accuracyof these surfaces, which is on the order of 51/2 millionths of an inchto produce a brilliance of the Class A type, it has .been heretoforenecessary to clamp the accurately formed rods and maintain the rods inthe clamp during the molding. lt has been found that if attempts weremade to reproduce the molding surface from the clamped rods as by anelectroformed reproduction, the optical quality and finish of theelectro-formed cores has been substantially reduced, resulting in asubstantial loss of brilliance and reflectivity.

The necessity for maintaining the rods in clamped relationship by meansof a mechanical clamp has seriously limited the design of the reflectorsthat can be made. lt therefore has not been possible to make reflectorsof Class A or Class B brilliance which had multiple facets, that is,multiple reflecting surfaces at a plurality of angles. This has been dueto the interference of the clamps of adjacent clusters. As a result, thereflectors that have been made with the desired degree of brilliancehave a very limited area or cone of reflectivity.

It is therefore an object of this invention to provide a novel apparatusfor making reflectors.

It is a further object of the invention to provide a mold for areilector which has multiple facets and therefore a greater angle ofreflectivity and at the same time has a high degree of rellectivebrilliance.

In the drawings:

FIG. l is a fragmentary plan view of a reflector surface utilized in theinvention.

FIG. 2 is a fragmentary partly diagrammatic sectional view through thereflector in FIG. 1.

tive view of a reilector embodying the invention.

FIG. 4 is a perspective View of a rod utilized in the invention.

FIG. 5 is a plan view of an apparatus utilized in the invention.

..50 FIG. 3 is a fragmentary partly diagrammatic perspec- 3,363,875Patented .lair-i. lG, i968 manner in which the core units are combinedto form a core sub-assembly.

FIG. 12 is an end elevation of a core sub-assembly.

FIG. 13 is a perspective view of the core sub-assembly shown in FIG. 12.

FIG. 14 is an end View of further assembly of the core sub-assembliesshown in FIGS. 12 and 13.

FIG. 15 is a further sub-assembly.

FIG. .16 is an end view of a core assembly.

FIG. 17 is an exploded perspective View of the unit shown in FIG. 16.

FIG. 18 is a view of the apparatus utilized in a modified step in themethod of making core units.

FIG. 19 is a plan view of the core unit made by the apparatus in FIG.18.

FIG. 20 is an end view of the core unit shown in FIG. 19.

FIG. 21 is an exploded perspective view showing the manner in which thecore units shown in FIGS. 19 and 2O are assembled to form a coreassembly.

FIGS. 22, 23 and 24 are perspective views of rod core assemblies formolds to produce reflectors embodying the invention.

FIG. 25 is an exploded perspective view of a modified core assembly.

FIG. 26 is a fragmentary perspective View of a modified core unit.

The type of reflector to Which the invention relates embodies areflecting surface such as shown in FIGS. l and 2. Referring to FIGS. land 2, the plastic or glass relector R comprises a smooth or otherwiseshaped outer surface S and an accurately formed inner surface formingrellecting surfaces that preferably intersect at 9i) degree angles inthe form of cubic corners or prisms C. Such reflectors are commonlycalled retrodirective types, since the light rays from an externalsource are redirected by reflections from the surfaces of the prisms Cback to the exterior, as shown by the light rays in FIG. 2. Reilectorsof this type are of particular use in automotive vehicles, alonghighways and airfield landing strips to reilect back to an approachingvehicle or airplane the light rays projected from a light and therebyserve as a guide or danger signal. The reflectors themselves may havelight sources positioned behind the prisms C.

Heretofore, accurate surfaces on such reflectors have been only possibleby assembling a plurality of accurately formed hexagonal rods 30 (FIG.4) into a bundle or unit by physically clamping the rods and maintainingthem clamped during the molding operation. The ends of the rods haveaccurately formed cubic corners 31 thereon against which the moltenplastic material is pressed to form the prisms C. Because of theinterference of the physical clamps that clamp the adjacent bundles orgroups of rods 3l), it has not heretofore been possible to produce areflector such as shown in FIG. 3 having a plurality of facets F atangles to one another and thereby provide a reflector which has a wideangle of rcllectivity. Herefofore, it has only been possible to producea reflector such as shown in FIG. 3 by an electroform core unit, whichdoes not have a molding surface sufiiciently accurate to produce therequired degree of brilliance.

In accordance with the apparatus of the present invention, a reflectorsuch as shown in FIG. 3 is produced by forming a plurality of bundles orgroups or rods 3l) which need not be maintained in clamped assembly byphysical clamps. These groups or rods, hereinafter referred to asunitary rod or core units, are xed to a core block in adjacent abuttingrelation to one another to form the core assembly that is used inproducing the multi-faceted rellector.

ln accordance with the invention, the unitary core units are made insuch a manner that the accuracy of the 3 shaped or cubed ends of therods is maintained undisturbed and, as a result, the reflector that ismade has the required high degree of brilliance.

The method of assembling the rod units in a unitary core may be betterunderstood by reference to FIGS. 5-10. A plurality of accurately formedrods 30 Which are generally hexagonal in cross section and have cubedends 31 are assembled in a bundle with the cubed ends 31 formed into thedesired molding surface which may be either planar or curved. The bundleof rods is then clamped tightly by means of a clamp 32 adjacent the endsofrods which are opposite the cubed ends 31. Clamp 32 comprises clampelements 33, 34 held together by bolts 35.

Each rod 30 has a length preferably of 1% to 1% inches and the cubedends 31 are formed and finished to high optical quality standards on theorder of 51/2 millionths of an inch.

The completely oriented cluster or bundle of rods, after being clampedtightly by clamp 32, is then clamped adjacent its cube ends 31 tightlyby another clamp 36. In the case of the rods having the lengthsheretofore mentioned, the distance d is preferably approximately 1/8inch and the distance e is preferably approximately B; inch (FIG. 7).

As a next step, the clamped cluster of rods is severed in the areabetween the clamps 32, 36 along the line L. In the case of the rodshaving the length heretofore mentioned, line L is preferably about 0716inch from the underside of the clamp 36.

This produces a clamped cluster of the shaped cube ends of the rods asshown in FIG. 8. As a next step, the ends opposite the cubed ends arefusion welded as at W in an inert atmosphere formed by inert gas to afusion depth sufficient to hold the rods in an assembled core unit afterthe clamps 36 are removed. At the same time, a liquid coolant is appliedto the cube ends 31 to maintain the cube ends 31 cooled during theWelding. Preferably, the coolant is applied by means of jets of liquidcoolant from a jet pipe 38 While the assembled clamp 36 and rods aresubstantially submerged in liquid coolant (FIG. 9). The fusion weldingis performed carefully in order to protect the optical quality of thesurfaces 31 of the rods from damage by the heat, oxidation ordiscoloration.

After the fusion welding, the clamped cluster with the clamp 36 inposition is heat treated to relieve all stresses in the rods which mayhave been introduced by the fusion Welding.

Next, the welded surface W is ground to a high degree of accuracy toform an accurately formed bottom surface 40 (FIG. 10). The accuracy ofthe surface 40 with respect to the axes of the rods is referencedagainst corresponding accurately formed surfaces 41, 42 on the clamps36.

After the surface 40 has been obtained, the clamp 36 is carefullyremoved, resulting in a unitary core unit 45 of rods, which isthereafter handled carefully to prevent damage to the cube ends of therods.

A plurality of the units can then be mounted on a base or block toprovide a multi-faceted core assembly.

In accordance with the invention, each core unit 45 preferably has theside surface 46 thereof accurately ground in a gradual taper or negativeangle from the cube ends to the opposite ends so that the core units 45are clamped against a base block, as shown diagrammatically in FIG. 11.The upper ends of the side surfaces 46 abut in tight relationship to oneanother. This provides an additional clamping pressure transverselyacross the cube ends of the rods when the core units are assembled in acore assembly. This additional clamping pressure prevents any of therods from loosening under the forces encountered in molding and alsoproduces a maximum it at the cluster adjoining surfaces 46, therebypreventing any of the molten material from Working into the area betweenthe surfaces 45 under the high molding pressures encountered in use.

One of the methods of assembling the core units 45 to form the coreassembly is shown in FIGS. 12-17. As shown in FIGS. 12 and 13, aplurality of core units 45 are successively mounted on wedge-shapedblocks 47 by tack welding as at The block 47 has surfaces 49, 50, 51 atvarious angles to one another. During tack welding, the core units 45are held in tightly adjacent relationship by clamps so that the sidesurfaces 46 having the negative angle produce a high pressure at theupper corners, as shown in FIG. 11. Each sub-assembly of a Wedge block4/ and core units 45 is xed to another subassembly by means of dovvelpins 52 and screws 53 extending into the blocks (FIG. 14). Successiveblocks 47 are assembled to each sub-assembly of blocks by pins 52 andscrews 53 (FIG. l5). Finally, the assembled blocks 47 and core units 45having the wedge units thereon are mounted on a base 54 by means ofscrews 55 that extend into threaded openings 56 of pins 57 that aredriven into openings 58 in the blocks (FIGS. 16 and 17).

The resultant core assembly can be utilized With a complementary mold toform a cavity into which molten material is injected to form theretiector.

Instead of mounting the core units on a base as shown in FIGS. 12-17, analternative method may be used such as shown in FIGS. 18-21.

After the accurately formed surface 40 has been provided, as shown inFIG. 10, an opening 60 is drilled and tapped through the surface 40. Theend of the opening of) is then fusion welded in an inert gas atmospherewhile liquid coolant is provided to the cube ends of the rods by iets(as in FIG. 9) in order to protect the surfaces from discoloration anddamage. The entire clamp structure is then heated in a heat treatingenclosure to relieve all stresses from the fusion Welding of the end ofthe opening 60, after which the clamp 36 is removed.

The entire cluster that forms a core unit 45 is carefully unclamped andhandled in such a manner as to prevent damage to the cubed ends of therods. The side surfaces 46 are then formed With a negative angle as inthe previous form of core unit and the core units are assembled on abase 61 by means of screws 62 that extend through threaded openings 63in the base into the threaded opening 6@ of the core unit. The base 61is formed With surfaces 64, 65, 66 at various angles corresponding tothe angularity required between the facets of the reflector which was tobe molded. During clamping into position, the adjacent faces 46 arebrought into position with the upper ends thereof in tightly clampingrelation, as shown diagrammatically in FIG. 1l.

The types of reflectors that can be molded by utilizing core units madein accordance with the invention vary in shape and can be such, `forexample, as shown in FIGS. 22, 23 and 24, having various curvaturestransversely and longitudinally.

The core units made in accordance with the invention have the furtheradvantage in that they can be used to produce a retiector which hasspaced reector portions Such as shown in FIG. 25. In other Words, thecore units may be made of various cross sections or ground after theyare made along their side surfaces to various shapes as shown in FIG.25.

In addition, the cube ends of the rods need not be in a fiat plane butmay be curved, as shown in FIG. 26.

It has been found that reflectors made in accordance with the inventioneasily meet the standards of Class A reflective `brillance 0f theSociety of Automotive Engineers.

We claim:

ll. A unitary rod core unit comprising a plurality of accurately formedrods assembled in side-by-side relationship,

each rod having a shaped end,

said shaped ends being accurately positioned to define a moldingsurface,

the lower ends of said rods being joined by fusion welding to hold saidrods in a unitary assembly for molding.

2. The unit set forth in claim l wherein said unit includes anaccurately formed surface at the ends of said rods remote from saidshaped ends.

3. The unit set forth in claim 1, said unit having a threaded openingtherein in a direction generally parallel to the axis of said rods,

the base of said opening being fusion welded.

4. rThe unit set forth in claim 3 wherein each said unit has the sidesurfaces thereof tapering inwardly from the shaped ends to the oppositeends in the direction of the axis of the rods.

5. The unit set forth in claim 4 including a base,

and means lfor supporting a plurality of said units on said base withthe portions of said surfaces which are adjacent said shaped ends inabutting relation.

6. The combination set forth in claim 5 wherein said lastmentioned meanscomprises spaced welds.

'7. A unitary rod core unit comprising a plurality of accurately formedhexagonal rods assembled in sideby-side relationship,

each rod having a cube end,

said cube ends being accurately positioned to define a molding surface,

the lower ends of said rods being joined by fusion Welding.

S. The combination set forth in claim 7 wherein said 30 the axis of therods tapering inwardly from the cube ends to the opposite ends.

10. The combination set forth in claim 8 wherein said rod unit has theside surfaces thereof in the direction of the axis of the rods taperingfrom the cube ends to the opposite ends.

11. A unitary rod core unit comprising a plurality of accurately formedrods assembled in side-by-side relationship, each rod having a shapedend, said shaped ends being accurately positioned to define a moldingsurface,

the lower ends of said rods being joined by fusion welding to hold saidrods in a unitary assembly for molding,

said core unit having at least one side surface thereof tapered.

12. The combination set forth in claim 11 wherein said unit includes anaccurately formed planar surface at the ends of said rods remote fromsaid molding surface.

13. The combination set forth in claim 12 including a base and means forclamping said rod unit to said base with said tapered surface and saidplanar surface in engagement with said `base.

References Cited UNITED STATES PATENTS 3,277,535 10/1966 Rupert.

FOREIGN PATENTS 133,138 6/ 1949 Australia. 156,617 5/1954 Australia.

494,480 10/1938 Great Britain.

I. HOWARD FLINT, JR., Primary Examiner.

1. A UNITARY ROD CORE UNIT COMPRISING A PLURALITY OF ACCURATELY FORMEDRODS ASSEMBLED IN SIDE-BY-SIDE RELATIONSHIP, EACH ROD HAVING A SHAPEDEND, SAID SHAPED ENDS BEING ACCURATELY POSITIONED TO DEFINE A MOLDINGSURFACE, THE LOWER ENDS OF SAID RODS BEING JOINED BY FUSION WELDING TOHOLD SAID RODS IN A UNITARY ASSEMBLY FOR MOLDING.